Question

Write a note on heterocyst.

Answer 1

Blue-green algae or cyanobacteria such as Nostoc, Anabaena possess specialized cells. These cells are called as heterocysts. These are modified cells which are formed from the vegetative cells. These are the sites for $N_2$ fixation. There is an enzyme in the heterocyst called as nitrogenase which helps in nitrogen fixation. These cells also perform oxygenic photosynthesis.